Effects of monensin and/or yeast culture fed in the diet or infused into the abomasum on rumen fermentation and concentrations of glucose, urea, insulin, gastrin and cholecystokinin in blood of sheep

Abstract

Monensin and yeast culture are known to alter rumen fermentation. Their modes of action appear to be different, and a recent study showed that the combination of both yeast culture (YC) and monensin stimulated weight gain in bulls by 12-13% over monensin alone (Spedding, 1990). However, Edwards et al. (1991) found no complementary effects between YC and avoparcin when they were combined in a silage diet for steers. In addition to its action in the rumen, monensin is known to affect post-ruminal digestion (Armstrong, 1984). Viable Saccharomyces cerevisiae have been isolated from the duodenal digesta of sheep fed YC (Newbold et al., 1990), suggesting that YC too might have post-ruminal effects. The aim of the current study was to assess the effect of monensin and/or yeast culture in the diet or infused into the abomasum on rumen fermentation and blood parameters, and also on digestive physiology by monitoring plasma gastrin, insulin and CCK-8 concentration.